The p21.sup.ras oncogene is a major contributor to the development and progression of human solid cancers and is mutated in 30% of all human cancers; Bolton et al., Annual Reports in Medicinal Chemistry, 29, 165-174 (1994); Bos, Cancer Res., 49, 4682 (1989).
In its normal, unmutated form, the ras protein is a key element of the signal transduction cascade directed by growth factor receptors in almost all tissues. See J. Avruch et al., TIBS (19), 279-283 (1994). Biochemically, ras is a guanine nucleotide binding protein, and cycling between a GTP-bound activated and a GDP-bound resting form is strictly controlled by ras' endogenous GTPase activity and other regulatory proteins. In the ras mutants in cancer cells, the endogenous GTPase activity is alleviated and, therefore, the protein delivers constitutive growth signals to downstream effectors such as the enzyme raf kinase. This leads to the cancerous growth of the cells which carry these mutants, Magnuson et al., Cancer Biology, 5, 247-253 (1994). It has been shown that inhibiting the effect of active ras by inhibiting the raf kinase signaling pathway by administration of deactivating antibodies to raf kinase or by co-expression of dominant negative raf kinase or dominant negative MEK, the substrate of raf kinase, leads to the reversion of transformed cells to the normal growth phenotype. See Daum et al., TIBS 196, 474-480 (1994), and Fridman et al., J. Biol. Chem., 269, 30105-30108 (1994). Kolch et al., Nature, 349, 426-428 (1991), have further indicated that inhibition of raf expression by antisense RNA blocks cell proliferation in membrane-associated oncogenes. Similarly, inhibition of raf kinase (by antisense oligodeoxynucleotides) has been correlated in vitro and in vivo with inhibition of the growth of a variety of human tumor types; Monia et al., Nature Medicine, 2(6):668-675 (1996).